Method and apparatus for achieving physical connection between the flux guide and the free layer and that insulates the flux guide from the shields

ABSTRACT

A method for making a tunnel valve head with a flux guide, a tunnel valve sensor having an isolated flux guide, and a magnetic storage system using a tunnel valve sensor having an isolated flux guide is disclosed. The tunnel valve senors is created by forming a tunnel valve at a first shield layer, the tunnel valve comprising a free layer distal to the first shield layer, depositing a first insulation layer over the first shield layer and around the tunnel valve, depositing a flux guide over the first insulation layer and coupling to the tunnel valve at the free layer, covering the flux guide with a second insulation layer and forming a second shield layer over the second insulation, wherein the flux guide and the free layer are physically isolated by the first and second insulation layers to prevent current shunts therefrom. The structure achieves physical connection between the flux guide and the free layer and insulates the flux guide from the shields. By separating the flux guide and the free layer from the shields, the shunting of current is prevented.

RELATED PATENT DOCUMENTS

This application is a divisional of U.S. patent application Ser. No.09/902,122, filed on Jul. 10, 2001 (SJO920010042US1), to which priorityis claimed under 35 U.S.C. § 120, and which is incorporated herein byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates in general to magnetoresistive (MR) heads forreading magnetically recorded data, and more particularly to a methodand apparatus for providing a structure that achieves physicalconnection between the flux guide and the free layer and that insulatesthe flux guide from the shields.

2. Description of Related Art

Magnetic recording is a key and invaluable segment of theinformation-processing industry. While the basic principles are onehundred years old for early tape devices, and over forty years old formagnetic hard disk drives, an influx of technical innovations continuesto extend the storage capacity and performance of magnetic recordingproducts. For hard disk drives, the areal density or density of writtendata bits on the magnetic medium has increased by a factor of more thantwo million since the first disk drive was applied to data storage.Since 1991, areal density has grown by the well-known 60% compoundgrowth rate, and this is based on corresponding improvements in heads,media, drive electronics, and mechanics.

Magnetic recording heads have been considered the most significantfactor in areal-density growth. The ability of these components to bothwrite and subsequently read magnetically recorded data from the mediumat data densities well into the Gbits/in² range gives hard disk drivesthe power to remain the dominant storage device for many years to come.

The heart of a computer is an assembly that is referred to as a magneticdisk drive. The disk drive includes a rotating magnetic disk, write andread heads that are suspended by a suspension arm above the rotatingdisk and an actuator that swings the suspension arm to place the readand write heads over selected circular tracks on the rotating disk. Theread and write heads are directly mounted on a slider that has anair-bearing surface (ABS). The suspension arm biases the slider intocontact with the surface of the disk when the disk is not rotating.However, when the disk rotates, air is swirled by the rotating diskadjacent the ABS causing the slider to ride on an air bearing a slightdistance from the surface of the rotating disk. The write and read headsare employed for writing magnetic impressions to and reading magneticimpressions from the rotating disk. The read and write heads areconnected to processing circuitry that operates according to a computerprogram to implement the writing and reading functions.

A magnetoresistive (MR) sensor detects magnetic field signals throughthe resistance changes of a sensing element, fabricated of a magneticmaterial, as a function of the strength and direction of magnetic fluxbeing sensed by the sensing element. Conventional MR sensors, such asthose used as a MR read heads for reading data in magnetic recordingdisk drives, operate on the basis of the anisotropic magnetoresistive(AMR) effect of the bulk magnetic material, which is typically permalloy(Ni₈₁Fe₁₉). A component of the read element resistance varies as thesquare of the cosine of the angle between the magnetization direction inthe read element and the direction of sense current through the readelement. Recorded data can be read from a magnetic medium, such as thedisk in a disk drive, because the external magnetic field from therecorded magnetic medium (the signal field) causes a change in thedirection of magnetization in the read element, which in turn causes achange in resistance of the read element and a corresponding change inthe sensed current or voltage.

An MTJ device has been proposed as a magnetoresistive read head formagnetic recording in U.S. Pat. No. 5,390,061. A magnetic tunneljunction (MTJ) device is comprised of two ferromagnetic layers separatedby a thin insulating tunnel barrier layer and is based on the phenomenonof spin-polarized electron tunneling. Such sensors are also referred totunnel valve sensors. In such sensors, one of the ferromagnetic layershas a higher saturation field in one direction of an applied magneticfield, typically due to its higher coercivity than the otherferromagnetic layer. The insulating tunnel barrier layer is thin enoughthat quantum mechanical tunneling occurs between the ferromagneticlayers. The tunneling phenomenon is electron-spin dependent, making themagnetic response of the MTJ a function of the relative orientations andspin polarizations of the two ferromagnetic layers.

In an MTJ read head, the free ferromagnetic layer, the tunnel barrierlayer and the fixed ferromagnetic layer all have their edges exposed atthe sensing surface of the head, i.e., the air-bearing surface (ABS) ofthe air-bearing slider if the MTJ head is used in a magnetic recordingdisk drive. It has been discovered that when the MTJ head is lapped toform the ABS, it is possible that material from the free and fixedferromagnetic layers will smear at the ABS and short out across thetunnel barrier layer. In addition, many antiferromagnets used to fix themagnetic moment of the fixed ferromagnetic layer contain manganese (Mn)which can corrode during the ABS lapping process. The tunnel barrierlayer is typically formed of aluminum oxide, which can also corrodeduring the ABS lapping process. Accordingly, an tunnel valve read headfor a magnetic recording system wherein the free ferromagnetic layeralso acts as a flux guide to direct magnetic flux from the magneticrecording medium to the tunnel junction has been proposed to solve theseproblems. In a magnetic recording disk drive embodiment, the fixedferromagnetic layer has its front edge recessed from the ABS while thesensing end of the free ferromagnetic layer is exposed at the ABS. Thefront edge of the tunnel barrier layer may also be recessed from theABS. Both the fixed and free ferromagnetic layers are in contact withopposite surfaces of the tunnel barrier layer but the free ferromagneticlayer extends beyond the back edge of either the tunnel barrier layer orthe fixed ferromagnetic layer, whichever back edge is closer to thesensing surface. This assures that the magnetic flux is non-zero in thetunnel junction region. The magnetization direction of the fixedferromagnetic layer is fixed in a direction generally perpendicular tothe ABS and thus to the disk surface, preferably by interfacial exchangecoupling with an antiferromagnetic layer. The magnetization direction ofthe free ferromagnetic layer is aligned in a direction generallyparallel to the surface of the ABS in the absence of an applied magneticfield and is free to rotate in the presence of applied magnetic fieldsfrom the magnetic recording disk. A layer of high coercivity hardmagnetic material adjacent the sides of the free ferromagnetic layerlongitudinally biases the magnetization of the free ferromagnetic layerin the preferred direction.

However, to prevent shunting of current, the flux guide needs to beinsulated. To achieve high efficiency, it is necessary that there be noseparation between the flux guide and the free layer.

It can be seen that there is a need for a method and apparatus forproviding a structure that achieves physical connection between the fluxguide and the free layer and that insulates the flux guide from theshields.

SUMMARY OF THE INVENTION

To overcome the limitations in the prior art described above, and toovercome other limitations that will become apparent upon reading andunderstanding the present specification, the present invention disclosesa method and apparatus for providing a structure that achieves physicalconnection between the flux guide and the free layer and that insulatesthe flux guide from the shields.

The present invention solves the above-described problems by separatingthe flux guide and the free layer to prevent the shunting of current.

A method in accordance with the principles of the present inventionincludes forming a tunnel valve at a first shield layer, the tunnelvalve comprising a free layer distal to the first shield layer,depositing a first insulation layer over the first shield layer andaround the tunnel valve, depositing a flux guide over the firstinsulation layer and coupling to the tunnel valve at the free layer,covering the flux guide with a second insulation layer and forming asecond shield layer over the second insulation, wherein the flux guideand the free layer are physically isolated by the first and secondinsulation layers to prevent current shunts therefrom.

Other embodiments of a method in accordance with the principles of theinvention may include alternative or optional additional aspects. Onesuch aspect of the present invention is that the depositing the firstinsulation layer over the first shield layer and around the tunnel valveis performed using a self-aligning process wherein regions of differentthicknesses are formed with a single masking step.

Another aspect of the present invention is that the flux guide isphysically connected to the free layer of the tunnel valve.

Another aspect of the present invention is that the covering the fluxguide with a second insulation layer is performed using a self-aligningprocess wherein regions of different thicknesses are formed with asingle masking step.

Another aspect of the present invention is that the flux guide increasesthe amount of magnetic flux in the tunnel valve.

Another aspect of the present invention is that the increase in theamount of magnetic flux in the tunnel valve enhances the output signalfo the tunnel valve.

Another aspect of the present invention is that the forming a tunnelvalve at a first shield layer further includes forming anantiferromagnetic (AFM) layer of electrically insulatingantiferromagnetic material, depositing a pinned layer of ferromagneticmaterial in contact with said AFM layer, said pinned layer makingelectrical contact with said first shield, forming a free layer offerromagnetic material and forming a tunnel junction layer ofelectrically insulating material between said pinned and free layers.

In another embodiment of the present invention, a tunnel valve sensor isdisclosed. The tunnel valve sensor includes a tunnel valve disposed at afirst shield layer, the tunnel valve comprising a free layer distal tothe first shield layer, a first insulation layer formed over the firstshield layer and around the tunnel valve, a flux guide deposited overthe first insulation layer, the flux guide being coupled to the tunnelvalve at the free layer, a second insulation layer covering the fluxguide; and a second shield layer deposited over the second insulation,wherein the flux guide and the free layer are physically isolated by thefirst and second insulation layers to prevent current shunts therefrom.

Another aspect of the present invention is that the flux guide isphysically connected to the free layer of the tunnel valve.

Another aspect of the present invention is that the flux guide increasesthe amount of magnetic flux in the tunnel valve.

Another aspect of the present invention is that the increase in theamount of magnetic flux in the tunnel valve enhances the output signalfo the tunnel valve.

Another aspect of the present invention is that the tunnel valve furtherincludes an antiferromagnetic (AFM) layer of electrically insulatingantiferromagnetic material, a pinned layer of ferromagnetic material incontact with said AFM layer, said pinned layer making electrical contactwith said first shield, a free layer of ferromagnetic material and atunnel junction layer of electrically insulating material disposedbetween said pinned and free layers.

In another embodiment of the present invention, a magnetic storagedevice is disclosed. The magnetic storage system includes a magneticrecording medium, an actuator for moving the tunnel valve sensor acrossthe magnetic recording disk so the tunnel valve sensor may accessdifferent regions of magnetically recorded data on the magneticrecording medium, a data channel coupled electrically to the tunnelvalve sensor for detecting changes in resistance of the tunnel valvesensor caused by rotation of the magnetization axis of the freeferromagnetic layer relative to the fixed magnetization of the pinnedlayer in response to magnetic fields from the magnetically recorded dataand a tunnel valve sensor disposed proximate the recording medium, thetunnel vavle sensor, includes a tunnel valve disposed at a first shieldlayer, the tunnel valve comprising a free layer distal to the firstshield layer, a first insulation layer formed over the first shieldlayer and around the tunnel valve, a flux guide deposited over the firstinsulation layer, the flux guide being coupled to the tunnel valve atthe free layer, a second insulation layer covering the flux guide and asecond shield layer deposited over the second insulation, wherein theflux guide and the free layer are physically isolated by the first andsecond insulation layers to prevent current shunts therefrom.

Another aspect of the present invention is that the flux guide isphysically connected to the free layer of the tunnel valve.

Another aspect of the present invention is that the flux guide increasesthe amount of magnetic flux in the tunnel valve.

Another aspect of the present invention is that the increase in theamount of magnetic flux in the tunnel valve enhances the output signalfo the tunnel valve.

Another aspect of the present invention is that wherein the tunnel valvefurther includes an antiferromagnetic (AFM) layer of electricallyinsulating antiferromagnetic material, a pinned layer of ferromagneticmaterial in contact with said AFM layer, said pinned layer makingelectrical contact with said first shield, a free layer of ferromagneticmaterial and a tunnel junction layer of electrically insulating materialdisposed between said pinned and free layers.

These and various other advantages and features of novelty whichcharacterize the invention are pointed out with particularity in theclaims annexed hereto and form a part hereof. However, for a betterunderstanding of the invention, its advantages, and the objects obtainedby its use, reference should be made to the drawings which form afurther part hereof, and to accompanying descriptive matter, in whichthere are illustrated and described specific examples of an apparatus inaccordance with the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Referring now to the drawings in which like reference numbers representcorresponding parts throughout:

FIG. 1 illustrates a storage system according to the present invention;

FIG. 2 illustrates one particular embodiment of a storage systemaccording to the present invention;

FIG. 3 illustrates a slider mounted on a suspension;

FIG. 4 is an ABS view of the slider and the magnetic head;

FIG. 5 is a cross-sectional schematic view of the integrated read/writehead which includes a MR read head portion and an inductive write headportion;

FIG. 6 is a section view of one embodiment of a tunnel valve read headas it would appear if taken through a plane whose edge is shown as line542 in FIG. 5 and viewed from the disk surface;

FIG. 7 illustrates a tunnel valve read head according to the presentinvention; and

FIG. 8 illustrates a flow chart of a method of making a tunnel valvehead with a flux guide according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

In the following description of the exemplary embodiment, reference ismade to the accompanying drawings which form a part hereof, and in whichis shown by way of illustration the specific embodiment in which theinvention may be practiced. It is to be understood that otherembodiments may be utilized as structural changes may be made withoutdeparting from the scope of the present invention.

The present invention provides a method and apparatus for providing astructure that achieves physical connection between the flux guide andthe free layer and that insulates the flux guide from the shields. Byseparating the flux guide and the free layer from the shields, theshunting of current is prevented.

FIG. 1 illustrates a storage system 100 according to the presentinvention. In FIG. 1, a transducer 110 is under control of an actuator120. The actuator 120 controls the position of the transducer 110. Thetransducer 110 writes and reads data on magnetic media 130. Theread/write signals are passed to a data channel 140. A system processor150 controls the actuator 120 and processes the signals of the datachannel 140. In addition, a media translator 160 is controlled by asystem processor 150 to cause the magnetic media 130 to move relative tothe transducer 110. The present invention is not meant to be limited toa particular type of storage system 100 or to the type of media 130 usedin the storage system 100.

FIG. 2 illustrates one particular embodiment of a storage system 200according to the present invention. In FIG. 2, a hard disk drive 200 isshown. The drive 200 includes a spindle 210 that supports and rotates amagnetic disk 214. The spindle 210 is rotated by a motor 220 that iscontrolled by a motor controller 230. A combined read and write magnetichead 240 is mounted on a slider 242 that is supported by a suspension244 and actuator arm 246. Processing circuitry 250 exchanges signals,representing such information, with the head 240, provides motor drivesignals for rotating the magnetic disk 214, and provides control signalsfor moving the slider to various tracks. A plurality of disks 214,sliders 242 and suspensions 244 may be employed in a large capacitydirect access storage device (DASD).

The suspension 244 and actuator arm 246 position the slider 242 so thatthe magnetic head 240 is in a transducing relationship with a surface ofthe magnetic disk 214. When the disk 214 is rotated by the motor 220 theslider 240 is supported on a thin cushion of air (air bearing) betweenthe surface of the disk 214 and the air-bearing surface (ABS) 248. Themagnetic head 240 may then be employed for writing information tomultiple circular tracks on the surface of the disk 214, as well as forreading information therefrom.

FIG. 3 illustrates a slider 310 mounted on a suspension 312. In FIG. 3first and second solder connections 304 and 306 connect leads from thesensor 308 to leads 313 and 314 on the suspension 312 and third andfourth solder connections 316 and 318 connect the coil 384 to leads 324and 326 on the suspension.

FIG. 4 is an ABS view of the slider 400 and the magnetic head 404. Theslider has a center rail 456 that supports the magnetic head 404, andside rails 458 and 460. The rails 456, 458 and 460 extend from a crossrail 462. With respect to rotation of a magnetic disk, the cross rail462 is at a leading edge 464 of the slider and the magnetic head 404 isat a trailing edge 466 of the slider.

FIG. 5 is a cross-sectional schematic view of the integrated read/writehead 525 which includes a MR read head portion and an inductive writehead portion. The head 525 is lapped to form an air-bearing surface(ABS), the ABS being spaced from the surface of the rotating disk 516 bythe air bearing as discussed above. The read head includes a MR sensor540 sandwiched between first and second gap layers G1 and G2 which are,in turn, sandwiched between first and second magnetic shield layers S1and S2. In a conventional disk drive, the MR sensor 540 is an AMRsensor. The write head includes a coil layer C and insulation layer 512which are sandwiched between insulation layers 511 and 513 which are, inturn, sandwiched between first and second pole pieces P1 and P2. A gaplayer G3 is sandwiched between the first and second pole pieces P1, P2at their pole tips adjacent to the ABS for providing a magnetic gap.During writing, signal current is conducted through the coil layer C andflux is induced into the first and second pole layers P1, P2 causingflux to fringe across the pole tips at the ABS. This flux magnetizescircular tracks on the rotating disk during a write operation. During aread operation, magnetized regions on the rotating disk inject flux intothe MR sensor 540 of the read head, causing resistance changes in the MRsensor 540. These resistance changes are detected by detecting voltagechanges across the MR sensor 540. The combined head 525 shown in FIG. 5is a “merged” head in which the second shield layer S2 of the read headis employed as a first pole piece P1 for the write head. In a piggybackhead (not shown), the second shield layer S2 and the first pole piece P1are separate layers.

The above description of a typical magnetic recording disk drive with anAMR read head, and the accompanying FIGS. 1-5, are for representationpurposes only. Disk drives may contain a large number of disks andactuators, and each actuator may support a number of sliders. Inaddition, instead of an air-bearing slider, the head carrier may be onewhich maintains the head in contact or near contact with the disk, suchas in liquid bearing and other contact and near-contact recording diskdrives.

According to the present invention, a MR read head uses a tunnel valvein place of the MR sensor 540 in the read/write head 525 of FIG. 5. FIG.6 is a section view of one embodiment of a tunnel valve read head 600 asit would appear if taken through a plane whose edge is shown as line 542in FIG. 5 and viewed from the disk surface. The tunnel valve read head600 of FIG. 6 is presented for the purposed of explaining the operationof the tunnel valve.

Referring to FIG. 6, the paper of FIG. 6 is a plane parallel to the ABSand through substantially the active sensing region, i.e., the tunneljunction, of the tunnel valve read head to reveal the layers that makeup the head. The tunnel valve read head includes an electrical lead 602formed on the gap layer G1 substrate, an electrical lead 604 below gaplayer G2, and the tunnel valve 608 formed as a stack of layers betweenelectrical leads 602, 604. The tunnel valve 608 includes a firstelectrode multilayer stack 610, an insulating tunnel barrier layer 620,and a top electrode stack 630. Each of the electrodes includes aferromagnetic layer in direct contact with tunnel barrier layer 620,i.e., ferromagnetic layers 618 and 632.

The base electrode layer stack 610 formed on electrical lead 602includes a seed or “template” layer 612 on the lead 602, a layer ofantiferromagnetic material 616 on the template layer 612, and a “fixed”ferromagnetic layer 618 formed on and exchange coupled with theunderlying antiferromagnetic layer 616. The ferromagnetic layer 618 iscalled the fixed layer because its magnetic moment or magnetizationdirection is prevented from rotation in the presence of applied magneticfields in the desired range of interest. The top electrode stack 630includes a “free” or “sensing” ferromagnetic layer 632 and a protectiveor capping layer 634 formed on the sensing layer 632. The sensingferromagnetic layer 632 is not exchange coupled to an antiferromagneticlayer, and its magnetization direction is thus free to rotate in thepresence of applied magnetic fields in the range of interest. Thesensing ferromagnetic layer 632 is fabricated so as to have its magneticmoment or magnetization direction (shown by arrow 633) orientedgenerally parallel to the ABS (the ABS is a plane parallel to the paperin FIG. 6) and generally perpendicular to the magnetization direction ofthe fixed ferromagnetic layer 618 in the absence of an applied magneticfield. The fixed ferromagnetic layer 618 in electrode stack 610 justbeneath the tunnel barrier layer 620 has its magnetization directionfixed by interfacial exchange coupling with the immediately underlyingantiferromagnetic layer 616, which also forms part of bottom electrodestack 610. The magnetization direction of the fixed ferromagnetic layer618 is oriented generally perpendicular to the ABS, i.e., out of or intothe paper in FIG. 6 (as shown by arrow tail 619).

Also shown in FIG. 6 is a biasing ferromagnetic layer 650 forlongitudinally biasing the magnetization of the sensing ferromagneticlayer 632, and an insulating layer 660 separating and isolating thebiasing layer 650 from the sensing ferromagnetic layer 632 and the otherlayers of the tunnel valve 608. The biasing ferromagnetic layer 650 is ahard magnetic material, such as a CoPtCr alloy, that has its magneticmoment (shown by arrow 651) aligned in the same direction as themagnetic moment 633 of the sensing ferromagnetic layer 632 in theabsence of an applied magnetic field. The insulating layer 660, which ispreferably alumina (Al₂O₃) or silica (SiO₂), has a thickness sufficientto electrically isolate the biasing ferromagnetic layer 650 from thetunnel valve 608 and the electrical leads 602, 604, but is still thinenough to permit magnetostatic coupling (shown by dashed arrow 653) withthe sensing ferromagnetic layer 632. The product M*t (where M is themagnetic moment per unit area of the material in the ferromagnetic layerand t is the thickness of the ferromagnetic layer) of the biasingferromagnetic layer 650 must be greater than or equal to the M*t of thesensing ferromagnetic layer 632 to assure stable longitudinal biasing.Since the magnetic moment of Ni_((100-X))—Fe_((x)) that is typicallyused in the sensing ferromagnetic layer 632 is about twice that of themagnetic moment of a typical hard magnetic material suitable for thebiasing ferromagnetic layer 650, such as CO₇₅Pt₁₃Cr₁₂, the thickness ofthe biasing ferromagnetic layer 650 is at least approximately twice thatof the sensing ferromagnetic layer 632.

A sense current I is directed from first electrical lead 602perpendicularly through the antiferromagnetic layer 616, the fixedferromagnetic layer 618, the tunnel barrier layer 620, and the sensingferromagnetic layer 632 and then out through the second electrical lead604. As described previously, the amount of tunneling current throughthe tunnel barrier layer 620 is a function of the relative orientationsof the magnetizations of the fixed and sensing ferromagnetic layers 618,632 that are adjacent to and in contact with the tunnel barrier layer620. The magnetic field from the recorded data causes the magnetizationdirection of sensing ferromagnetic layer 632 to rotate away from thedirection 633, i.e., either into or out of the paper of FIG. 6. Thischanges the relative orientation of the magnetic moments of theferromagnetic layers 618, 632 and thus the amount of tunneling current,which is reflected as a change in electrical resistance of the tunnelvalve 608. This change in resistance is detected by the disk driveelectronics and processed into data read back from the disk. The sensecurrent is prevented from reaching the biasing ferromagnetic layer 650by the electrical insulating layer 660, which also insulates the biasingferromagnetic layer 650 from the electrical leads 602, 604.

In a magnetic recording device the read head senses flux from smallmagnetized regions or magnetic bits written into a thin film magneticmedium above which the head is suspended. Increased capacity disk drivesare achieved in part by higher magnetic bit areal densities. Thus thearea of each magnetic region or bit must be decreased but this therebygives rise to reduced magnetic flux. Magnetic recording heads which cansense reduced magnetic flux with greater output signal are therebyrequired for higher performance and higher capacity magnetic recordingdisk drives.

FIG. 7 illustrates a tunnel valve read head 700 according to the presentinvention. In FIG. 7, a tunnel valve 710 is patterned at a first shieldlayer 712. Insulation 720 is deposited using the self-aligned process. Aflux guide 730 is deposited so that it overlaps with and is coupled tothe tunnel valve 710, but does not completely extend over the tunnelvalve 710. The flux guide 730 is then covered with insulation 740 usinga self-aligned process. Self-aligned processes allow a feature to bedefined without precise contact alignment. As with the otherself-aligned processes, a first feature is patterned by a backsideprocess step. Then a second feature is defined by a second backsideprocess step. This second backside process step uses an aspect of thefirst process step to define the second feature. After depositing theinsulation over the flux guide, the second shield 750 is formed.

The flux guide 730 thus makes physical connection with the free layer732 of the tunnel valve 710 while the flux guide 730 is insulated fromthe shields 712, 750. By separating the flux guide 730 and the freelayer 732 from the shields 712, 750, the shunting of current isprevented. Thus, the flux guide 730 increases the amount of magneticflux in the active region of the sensor 700. Consequently, the outputsignal of the tunnel valve sensor 700 with the flux guide 730 isenhanced by the amount of extra flux in the active region of the sensor700.

FIG. 8 illustrates a flow chart 800 of a method of making a tunnel valvehead with a flux guide according to the present invention. In FIG. 8, atunnel valve is patterned at a first shield layer 810. Insulation isdeposited using a self-aligned process 820. A flux guide is deposited830 so that it overlaps with tunnel valve, but does not completelyextend over the tunnel valve. The flux guide is then covered withinsulation using a self-aligned process 840. After depositing theinsulation over the flux guide, the second shield is formed 850.

The foregoing description of the exemplary embodiment of the inventionhas been presented for the purposes of illustration and description. Itis not intended to be exhaustive or to limit the invention to theprecise form disclosed. Many modifications and variations are possiblein light of the above teaching. It is intended that the scope of theinvention be limited not with this detailed description, but rather bythe claims appended hereto.

1. A method for making a tunnel valve head with a flux guide,comprising: forming a tunnel valve at a first shield layer, the tunnelvalve comprising a free layer distal to the first shield layer;depositing a first insulation layer over the first shield layer andaround the tunnel valve; depositing a flux guide over the firstinsulation layer and coupling to the tunnel valve at the free layer;covering the flux guide with a second insulation layer; and forming asecond shield layer over the second insulation, wherein the flux guideand the free layer are physically isolated by the first and secondinsulation layers to prevent current shunts therefrom.
 2. The method ofclaim 1 wherein the depositing the first insulation layer over the firstshield layer and around the tunnel valve is performed using aself-aligning process wherein regions of different thicknesses areformed with a single masking step.
 3. The method of claim 1 wherein theflux guide is physically connected to the free layer of the tunnelvalve.
 4. The method of claim 1 wherein the covering the flux guide witha second insulation layer is performed using a self-aligning processwherein regions of different thicknesses are formed with a singlemasking step.
 5. The method of claim 1 wherein the flux guide increasesthe amount of magnetic flux in the tunnel valve.
 6. The method of claim1 wherein the increase in the amount of magnetic flux in the tunnelvalve enhances the output signal fo the tunnel valve.
 7. The method ofclaim 1 wherein the forming a tunnel valve at a first shield layerfurther comprises: forming an antiferromagnetic (AFM) layer ofelectrically insulating antiferromagnetic material; depositing a pinnedlayer of ferromagnetic material in contact with said AFM layer, saidpinned layer making electrical contact with said first shield; forming afree layer of ferromagnetic material; and forming a tunnel junctionlayer of electrically insulating material between said pinned and freelayers.